Maneuvering system having inner force sense presenting function

ABSTRACT

A compact, lightweight manipulation system that excels in operability and has a force feedback capability is provided. When automatic operation of a slave manipulator  105  that follows manual operation of a master manipulator  101  is bilaterally controlled by means of communication, the force acting on the slave manipulator is fed back to the master manipulator by operating the master manipulator primarily under electrically-driven speed control and the slave manipulator primarily under pneumatically-driven force control. Therefore, in the master manipulator, it is not necessary to compensate for the dynamics and the self-weight of the master manipulator in the motion range of a user, allowing highly accurate, broadband positional control, which is specific to an electrically-driven system, and in the slave manipulator, nonlinearity characteristics specific to a pneumatically-driven system presents passive softness, provides a high mass-to-output ratio, and produces a large force.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application claiming priorityunder 35 U.S.C. 120 from co-pending U.S. patent application Ser. No.12/529,515 entitled “MANEUVERING SYSTEM HAVING INNER FORCE SENSEPRESENTING FUNCTION”. The entire disclosure of the aforesaid applicationis hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a manipulation system in whichautomatic operation of a slave manipulator that follows manual operationof a master manipulator is bilaterally controllable by means ofcommunication, and particularly to a manipulation system having a forcefeedback capability.

BACKGROUND OF THE INVENTION

In recent years, surgical operations have been widely practiced in theform of endoscopic surgery to improve QOL (Quality of Life), such asreduction in patient's pain, hospitalization period, and size of thescar associated with the surgery. Endoscopic surgery is performed insuch a way that an operator inserts forceps or other related toolsthrough a thin tube (trocar) and performs the surgery while observingimages from a laparoscope. Since the scar is smaller than that in opensurgery, the burden on the patient is smaller. However, since theoperator moves the forceps or other related tools using the abdominalwall as a pivotal point, sufficient degrees of freedom are not providedat the tip of the forceps and hence it is not easy to freely approachthe site to be treated. Such a situation requires a highly skilledoperator. To reduce the burden on the operator, studies on multi-DOFforceps system have been actively underway, in which robotics technologyis used to impart multiple degrees of freedom to the tip of forceps.

The master-slave concept used in commercially available multi-DOFforceps systems has advantages of, for example, capability of remotelyand intuitively operating the forceps. To provide more accurate, saferworkability, it is desirable to provide force feedback to the operator.To this end, studies on forceps with a force sensor provided in thevicinity of the tip of the forceps are underway. However, such amulti-DOF forceps system using electric actuators to drive the masterand slave portions not only cannot feed a minute force back to theoperator because of a high reduction ratio, but also has an insufficientmovable range and results in a bulky apparatus. Further, attaching aforce sensor to the forceps is not an easy task in consideration ofpractical factors, such as reduction in size, sterilization, andcalibration.

To address the above problems, the inventors of the present applicationhave conducted studies on multi-DOF forceps systems, in which pneumaticactuators are used to drive the master and slave portions. A pneumaticactuator, which has nonlinear characteristics, is inferior to anelectric actuator in terms of controllability, but has advantages of,for example, presenting passive softness, having a high mass-to-outputratio, and producing a large force without a reduction gear train. Forexample, a multi-DOF forceps system has been proposed (see thenon-patent document 1: “Bilateral control of multi-DOF forceps systemhaving force sensing capability using pneumatic servo technology”, JapanSociety of Computer Aided Surgery, pp. 25-31, (2005), Kotaro Tadano,Kenji Kawashima), in which the slave portion includes a 3-DOF forcepsmanipulator using pneumatic cylinders and the pressure in each of thepneumatic cylinders is used to estimate the external force acting on thetip of the forceps instead of using a force sensor. The entiredisclosures of the aforesaid non-patent reference 1 are incorporatedherein by reference. Further, a multi-DOF forceps system has beenproposed (see the non-patent document 2: “Development of master-slavesystem having force feedback capability using pneumatically-drivenmulti-DOF forceps: Development of manipulator for holding forceps”,Conference on Robotics and Mechatronics, 1A1-A03, (2006), Kotaro Tadano,Kenji Kawashima), which includes a 3-DOF pneumatic manipulator thatholds and drives the 3-DOF forceps manipulator described in thenon-patent document 1 in a region outside the abdomen. The entiredisclosures of the aforesaid non-patent reference 2 are incorporatedherein by reference.

However, in the multi-DOF forceps systems proposed in the abovementioned study, the forceps manipulator has only three degrees offreedom, which does not allow the motion of the human hand to bereproduced. In the multi-DOF forceps systems described in the non-patentdocuments 1 and 2, the forceps manipulator includes a mechanism thatconverts the linear motion of a pneumatic cylinder into rotationalmotion, so that reduction in weight of the forceps manipulator isdifficult to achieve. Further, the master and the slave portions areconfigured in the same manner (both are controlled pneumatically), whichdoes not necessarily provide an optimum structure in terms ofoperability.

The invention has been conceived and completed through the abovementioned studies conducted by the inventors of the present application.An object of the invention is to provide a compact, lightweightmanipulation system that excels in operability and has a force feedbackcapability.

SUMMARY OF THE INVENTION

To achieve the above object, the manipulation system having a forcefeedback capability according to a primary aspect of the invention is amanipulation system having a force feedback capability comprising amaster manipulator and a slave manipulator connected to each other in abilaterally controllable manner,

-   -   wherein a position and an orientation of a tip section of said        slave manipulator is controlled in accordance with manual        operation on an input unit of said master manipulator performed        by an operator;    -   said master manipulator is operated primarily under        electrically-driven speed control and the slave manipulator is        operated primarily under pneumatically-driven force control, and        an external force acting on the tip section of said slave        manipulator is fed back in to said master manipulator; and    -   said slave manipulator comprises a drive mechanism for moving        the tip section to a desired position with desired degrees of        freedom, and at least one pneumatic actuator for driving said        drive mechanism,    -   said manipulation system comprising:    -   an external force estimation section to estimate an external        force acting on the tip section of said slave manipulator from a        motion of said pneumatic actuator;    -   a master manipulator drive control unit to output, as a reactive        force given to the operator, a force feedback of an external        force acted on the tip section by driving the input section of        said slave manipulator based on the estimated value obtained,        obtain a target position/orientation (xm) for the tip section of        said slave manipulator from an opposing force (fm) to the        reactive force applied by the operator, and provide the obtained        target position/orientation to said slave manipulator; and    -   a slave manipulator drive control unit to control the position        and orientation of the tip section of said slave manipulator        based on the target position/orientation received from said        master manipulator drive control unit.

According to this configuration, while the slave manipulator uses asystem that primarily operates under pneumatically-driven force control,a system that primarily operates under electrically-driven speed controlis employed for the master manipulator. Furthermore, with the estimationunit to estimate an external force acted on the tip of the slavemanipulator, a force feedback is provided by driving the mastermanipulator based on the estimated value.

This makes it not necessary in the master manipulator to compensate forthe dynamics and the self-weight of the master manipulator in the motionrange of a user, allowing highly accurate, broadband positional control,which is specific to an electrically-driven system, and in the slavemanipulator, nonlinearity characteristics specific to apneumatically-driven system presents passive softness, provides a highmass-to-output ratio, and produces a large force.

According to one preferred embodiment of the present invention, themanipulation system having a force feedback capability is provided,wherein said slave manipulator comprises:

-   -   a drive torque calculation unit to calculate a first drive        torque to be generated by said pneumatic actuator based on said        target position/orientation received from the master        manipulator;    -   an inverse dynamics calculation unit to obtain a second drive        torque to be generated by said pneumatic actuator, wherein speed        generated by operation on the input unit of the master        manipulator by the operator and an acceleration speed obtained        from the speed are used as input values and applied in an        equation representing an inverse dynamics of said slave        manipulator;    -   a target drive torque calculation unit to obtain a target drive        torque to be given to said pneumatic actuator from the first        drive torque obtained in the drive torque calculation unit and        the second drive torque obtained in the inverse dynamics        calculation unit; and    -   a pneumatic cylinder control unit for moving the position of        said tip section, by controlling an amount and speed of air        supplied to a cylinder based on the target drive torque obtained        by the target drive torque calculation unit, thereby moving the        position of said tip section.

According to another embodiment of the present application, themanipulation system having a force feedback capability is provided,wherein

-   -   said external force estimation unit estimates said external        force from a pressure difference between both chambers of said        pneumatic actuator using a disturbance observer including an        inverse dynamics model from said pneumatic actuator to the tip        section.

According to yet another embodiment of the present application, themanipulation system having a force feedback capability is provided,wherein the slave controller employs a force-based impedance control inwhich a motion control loop includes a force control loop; and

-   -   said external force estimation unit estimates said external        force from the first drive torque to be generated in said        pneumatic actuator based on said target position/orientation.

According to yet another embodiment of the present application, themanipulation system having a force feedback capability is provided,wherein said drive torque calculation unit calculates a force (fdr) tobe generated at the tip end of said slave manipulator with a formula offdr=Kd(xs−xm)+Bd dxs/dt

-   -   wherein    -   Kd is a set stiffness of the slave manipulator,    -   xs is a position and orientation of the tip end of the slave        manipulator,    -   xm is a position and orientation of the tip end of the master        manipulator, and    -   Bd is a set viscosity of the slave manipulator; and    -   wherein said inverse dynamics calculation unit calculates the        target drive torque value τdrref with an equation of        τdrref=−Js(transposition)fdr+Z(qs,dqs/dt,d ² qs/dt ²);    -   wherein    -   Js is a Jacobi matrix representing a transition from the        displacements of the joints to the displacement of the tip        position of the slave manipulator,    -   Z is an inverse dynamics function for the slave manipulator, and    -   qs is a displacement of each joint of the slave manipulator; and        wherein said inverse dynamic calculation unit uses said target        position/orientation received from the main manipulator control        unit as a value for qs, dqs/dt, d²qs/dt², rather than the        displacement value qs of the slave manipulator.

Furthermore, the manipulation system is characterized in that the mastermanipulator includes a 3-DOF translation unit and a 4-DOF orientationunit connected to the translation unit, and the slave manipulatorincludes a 3-DOF holding unit and a 4-DOF grip unit held by the holdingunit. Such a configuration allows the motion of the human hand on themaster manipulator side to be reproduced on the slave manipulator side.Further, the manipulation system is characterized in that thetranslation unit, the orientation unit, the holding unit, and the gripunit are configured as a delta mechanism, a gimbal mechanism, acombination of a parallel link mechanism and a gimbal mechanism, and awire mechanism, respectively. The master manipulator and the slavemanipulator are thus configured differently from each other, so that theshapes thereof can be optimized in terms of operability. Further, themanipulation system is characterized in that the grip unit includespneumatic rotary actuators and wires connected to the pneumaticactuators, and the grip unit is driven by pulling motions of the wiresin response to the motions of the pneumatic actuators. The grip unit cantherefore directly transmit the swing motions of the pneumaticactuators, so that the weight of the slave manipulator can be reduced.

Further more, the manipulation system is characterized in that the forceacting on the grip unit is estimated from the drive forces of thepneumatic actuators by making use of the back drivability thereof. Noforce sensor is therefore required on the grip unit, thereby providingadvantages of reducing the size of the grip unit, making disinfection ofthe grip unit easy, and eliminating the need for calibration of the gripunit. The manipulation system is characterized in that compliance-basedcontrol is applied to the slave manipulator. Therefore, the slavemanipulator will not produce an excessive force.

Further, the manipulation system is characterized in that position-basedimpedance control in which a force control loop includes a motioncontrol loop is applied to the master manipulator, and force-basedimpedance control in which a motion control loop includes a forcecontrol loop is applied to the slave manipulator. Therefore, the slavemanipulator can be stably operated by imparting a moderate viscosityeffect to the master manipulator. Further, the manipulation system ischaracterized in that automatic operation of the slave manipulator thatfollows manual operation of the master manipulator is bilaterallycontrolled by means of wired communication. The master manipulator cantherefore remotely operate the slave manipulator by means of theInternet.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram showing a manipulationsystem having a force feedback capability according to an embodiment ofthe invention;

FIG. 2 is a perspective view showing the exterior of the mastermanipulator shown in FIG. 1;

FIG. 3 is a perspective view showing the translation unit shown in FIG.2;

FIG. 4 is a perspective view showing the orientation unit shown in FIG.2;

FIG. 5 is a perspective view showing the exterior of the slavemanipulator shown in FIG. 1;

FIG. 6 is a perspective view showing the holding unit shown in FIG. 5and also shows a pneumatic circuit for driving a pneumatic cylinder;

FIG. 7 is a perspective view showing the grip unit shown in FIG. 5;

FIG. 8 is a perspective view showing the forceps showing in FIG. 7;

FIG. 9 is, a perspective view showing the forceps holding unit shown inFIG. 7; and

FIG. 10 is a control block diagram of the multi-DOF forceps system.

FIG. 11 is a control block diagram for the multi-DOF forceps system.

FIG. 12 is a control block diagram for the multi-DOF forceps system.

FIG. 13 is a block diagram showing the multi-DOF forceps system.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention will be described with reference to thedrawings. The embodiment, which will be described below, does not limitthe inventive aspects according to the claims, and of all thecombinations of the features described in the embodiment are notnecessarily essential in providing means for solving the problems.

FIG. 1 is a schematic configuration diagram showing a manipulationsystem having a force feedback capability according to an embodiment ofthe invention. The manipulation system having a force feedbackcapability is a multi-DOF forceps system 100 including a mastermanipulator 101, a master controller 103, a slave manipulator 105, and aslave controller 107. The multi-DOF forceps system 100 is a remotemanipulation system in which automatic operation of the slavemanipulator 105 that follows manual operation of the master manipulator101 is remotely controllable by means of wired communication between themaster controller 103 and the slave controller 107.

The master manipulator 101 primarily operates under electrically-drivenpositional control using electric actuators, and includes a 3-DOFtranslation unit 110 configured as a delta mechanism and a 4-DOForientation unit 120 connected to the translation unit 110 andconfigured as a gimbal mechanism. On the other hand, the slavemanipulator 105 primarily operates under pneumatically-driven forcecontrol using pneumatic actuators, and includes a 3-DOF holding unit 150configured as a combination of a parallel link mechanism and a gimbalmechanism and a 4-DOF grip unit 160 held by the holding unit 150.

Use of an electric actuator, particularly a combination of a highreduction-ratio gear train and an electric motor, has advantages overthe case where a pneumatic cylinder is used, for example, in that highlyaccurate, broadband positional control is possible, and that applyingmotion control-based force control eliminates the need for compensationfor the dynamics and the self-weight of the master manipulator 101 inthe motion range of the operator. On the other hand, a pneumaticactuator, which has nonlinear characteristics, is inferior to anelectric actuator in terms of controllability, but has advantages, forexample, presenting passive softness, having a high mass-to-outputratio, and producing a large force without a reduction gear train.

The master controller 103 includes a computer 31 and a servo amplifier32. The slave controller 107 includes a computer 71, a servo valve 72,an air supplier 73, and a pressure gauge 74. The computer 31 in themaster controller 103 sends a tip position signal (a target positionsignal for the tip position of the slave manipulator, that is the tip ofthe grip unit 160), which is obtained by performing kinetic computationon a signal SPM from each encoder in the master manipulator 101, to thecomputer 71 in the slave controller 107 using UDP/IP communication. Thecomputer 71 in the slave controller 107 sends a control signal SCS tothe servo valve 72 based on the received position signal. The servovalve 72 adjusts compressed air CPA from the air supplier 73 based onthe received control signal SCS, and supplies the adjusted compressedair to the slave manipulator 105, so that the operation of the slavemanipulator 105 is automatically controlled to follow the manualoperation of the master manipulator 101.

On the other hand, the computer 71 in the slave controller 107 sends acalculated target value of the force produced at the tip (an estimatedvalue of an external force acted on the tip position of the slavemanipulator, that is the tip of the grip unit 160) to the computer 31 inthe master controller 103 using UDP/IP communication. The computer 31 inthe master controller 103 sends a control signal SCM to the servoamplifier 32 based on the received force signal. Based on the receivedcontrol signal SCM, the servo amplifier 32 feeds the force acting on theslave manipulator 105 back to the master manipulator 101.

FIG. 2 is a perspective view showing the exterior of the mastermanipulator 101. FIG. 3 is a perspective view showing the translationunit 110. FIG. 4 is a perspective view showing the orientation unit 120.In the master manipulator 101, as shown in FIG. 2, the orientation unit120 is fixed to the translation unit 110 with screws, which is in turnfixed to, for example, a housing (not shown) with screws. The mastermanipulator 101 is similar to the slave manipulator 105 in that thenumber of degrees of freedom is seven, but differs from the slavemanipulator 105 in that the master manipulator 101 uses a parallel linkmechanism and has a compact structure.

The translation unit 110 includes a circular mounting plate 111, threemotors 112, three links 113, three sets of parallel links 114, and atriangular fixture plate 115 as shown in FIGS. 2 and 3. The mountingplate 111 has a plurality of through holes 111 a drilled in the vicinityof the outer circumferential edge at uniform angular intervals, andscrews 111 b are inserted into the through holes 111 a to fix themounting plate 111, for example, to a housing. The three motors 112 aredisposed on the mounting plate 111 and fixed thereto with screws atuniform angular intervals (120 degrees) along a circumferential lineinside the outer circumferential edge in such a way that each of themotor shafts 112 a is oriented along a tangential line of the mountingcircumferential line. Each of the motors 112 is an AC servo motor with aharmonic gear transmission and an encoder built therein.

The link 113 is assembled in such a way that one end (rear end) thereofis fixed to the motor shaft 112 a and the other end (front end) issupported by a bearing 113 a in such a way that the bearing 113 abecomes perpendicular to the axis of the link. The parallel link 114includes two links 114 a and two link shafts 114 b, and adjacent ends ofthe two links 114 a are rotatably supported at both ends of the two linkshaft 114 b in such a way that the two links 114 a can be translatedwith a predetermined distance maintained therebetween. One of the linkshafts 114 b fits in the bearing 113 a attached to the tip of the link113. The fixture plate 115 is fixed in such a way that a bearing 115 adisposed at each apex of the triangle is oriented parallel to the axisof the beating 113 a attached to the link 113. The other link shaft 114b fits in the bearing 115 a fixed to each apex of the fixture plate 115.

The thus configured translation unit 110 is a delta mechanism havingthree degrees of freedom in total, that is, having the link 113 beingrotatable around the motor shaft 112 a of the motor 112 in the directionindicated by the arrow “a” in FIG. 3, the parallel link 114 beingrotatable around the tip of the link 113 in the same direction as therotational direction “a” of the link 113 and in the directionperpendicular thereto indicated by the arrow “b” in FIG. 3, and thefixture plate 115 being rotatable around the tip of the parallel link114 in the same direction as the rotational direction “a” of the link113. The translation unit 110 is therefore characterized in that itproduces a large translation force and maintains the same orientationindependent of its position.

The orientation unit 120 includes, as shown in FIGS. 2 and 4, anattachment plate 121 that is L-shaped in the side view, a first motor122, a first motor fixture plate 123 that is U-shaped in the side view,a second motor 124, a second motor fixture plate 125 that is L-shaped inthe side view, a third motor 126, a third motor fixture plate 127 thatis L-shaped in the side view, a cylindrical rotating arm 128, a forcesensor 129, a force sensor fixture plate 130 that is L-shaped in theside view, a rectangular column-like manipulation finger support arm131, and a rod-like manipulation finger 132. The attachment plate 121has a plurality of through holes 121 a drilled in one end thereof, andscrews 121 b are inserted into the through holes 121 a to fix theattachment plate 121 to the fixture plate 115. The first motor fixtureplate 123, to which the first motor 122 is fixed with screws, is fixedto the other end of the attachment plate 121 with screws in such a waythat the motor shaft 122 a is oriented parallel to the fixture plate115.

One end of the second motor fixture plate 125 is fixed to the motorshaft 122 a of the first motor 122, and the second motor 124 is fixed tothe other end of the second motor fixture plate 125 with screws in sucha way that the motor shaft 124 a is oriented perpendicular to the motorshaft 122 a of the first motor 122. One end of the third motor fixtureplate 127 is fixed to the motor shaft 124 a of the second motor 124, andthe third motor 126 is fixed to the other end of the third motor fixtureplate 127 with screws in such a way that the motor shaft 126 a isoriented perpendicular to the motor shaft 122 a of the first motor 122and the motor shaft 124 a of the second motor 124. The rear end of therotating arm 128 is connected and fixed to the motor shaft 126 a of thethird motor 126 in such a way that the axial direction of the rotatingarm 128 is oriented in the axial direction of the motor shaft 126 a ofthe third motor 126.

The force sensor 129 is fixed to the tip of the rotating arm 128 via theforce sensor fixture plate 130 in such a way that the rotating shaft 129a of the force sensor 129 is oriented perpendicular to the motor shaft126 a of the third motor 126. The manipulation finger support arm 131 issupported at the tip of the rotating arm 128 in such a way that the rearend of the manipulation finger support arm 131 is rotatable around therotating shaft 129 a of the force sensor 129. The manipulation finger132 includes a hollow cylindrical body 132 a and a solid cylindricalslider 132 b that is inserted through the body 132 a and slidable in theaxial direction. The tip of the body 132 a is rotatably supported at thetip of the manipulation finger support arm 131 in the same direction asthe rotating shaft 129 a of the force sensor 129. The tip of the slider132 b is inserted and secured in a hole 128 a drilled in a substantiallycentral area of the rotating arm 128. Each of the first motor 122, thesecond motor 124, and the third motor 126 is an AC servo motor with aharmonic gear transmission and an encoder built therein. The forcesensor 129 is a six-axis force sensor capable of detecting translationalforces in three axial directions perpendicular to one another andmoments around the three axes.

The thus configured orientation unit 120 is a serial gimbal mechanismhaving four degrees of freedom in total, that is, having the secondmotor fixture plate 125 being rotatable around the motor shaft 122 a ofthe first motor 122 in the direction a in FIG. 4, the third motorfixture plate 127 being rotatable around the motor shaft 124 a of thesecond motor 124 in the direction β in FIG. 4, the rotating arm 128being rotatable around the motor shaft 126 a of the third motor 126 inthe direction .gamma. in FIG. 4, the manipulation finger support arm 131being rotatable around the rotating shaft 129 a of the force sensor 129in the direction δ in FIG. 4, and the body 132 a of the manipulationfinger 132 being slidable in the axial direction (the direction A inFIG. 4) along the slider 132 b when operated by the operator. Theorientation unit 120 is therefore characterized by its broad movablerange that covers the motion of the human hand.

FIG. 5 is a perspective view showing the exterior of the slavemanipulator 105. FIG. 6 is a perspective view showing the holding unit150. FIG. 7 is a perspective view showing the grip unit 160. In theslave manipulator 105, as shown in FIG. 5, the grip unit 160 is fixed tothe holding unit 150 with screws, which is in turn fixed to, forexample, a housing (not shown) with screws. The slave manipulator 105 issimilar to the master manipulator 101 in that the number of degrees offreedom is seven, but differs from the master manipulator 101 in thatthe slave manipulator 105 uses a combination of two sets of parallellink mechanisms and a gimbal mechanism as well as a wire mechanism andhas a compact structure.

As shown in FIGS. 5 and 6, the holding unit 150 includes a rectangularbase plate 151, a parallel link support shaft 152, two sets of parallellinks 153, a grip unit support base 154, three pneumatic cylinders(pneumatic actuators) 155, 156, and 157, and three cylinder fixtureplates 158 a, 158 b, and 158 c. Two bearings 151 a are disposed on andfixed to the base plate 151 with a predetermined distance therebetween.The two bearings 151 a rotatably support the parallel link support shaft152. A rod support 151 b, which rotatably supports a block 155 ab fixedto the tip of the rod 155 a of the first pneumatic cylinder 155, is alsodisposed on and fixed to the base plate 151 between the bearings 151 a.The body 155 b of the first pneumatic cylinder 155 is supported by oneend of the cylinder fixture plate 158 a, which is L-shaped in the sideview, and the other end thereof is fixed to a substantially centralportion of the parallel link support shaft 152.

One end of each of two links 153 a and 153 b, which form one of theparallel links 153, is rotatably supported at the corresponding end ofthe parallel link support shaft 152. With the two links 153 a and 153 bheld parallel to each other, one end of a link 153 c, which is part ofthe other parallel link 153, is rotatably supported at the other end ofthe link 153 b, and a substantially central portion of the link 153 c isrotatably supported at a substantially central portion of the link 153a. One end of a link 153 d, which is part of the other parallel link153, is rotatably supported at the other end of the link 153 a. With thetwo links 153 c and 153 d held parallel to each other, the other ends ofthe links 153 c and 153 d are rotatably supported by the cylinderfixture plate 151.

The body 156 b of the second pneumatic cylinder 156 is supported by oneend of the cylinder fixture plate 158 b, which is L-shaped in the sideview, and the other end thereof is rotatably supported at the portionwhere the links 153 b and 153 c are rotatably supported. A block (notshown) fixed to the tip of the rod 156 a of the second pneumaticcylinder 156 is rotatably supported between the two ends of the link 153a. The body 157 b of the third pneumatic cylinder 157 is supported byone end of the cylinder fixture plate 158 c, which is L-shaped in theside view, and the grip unit support base 154 is attached to thecylinder fixture plate 158 c in a slidable manner in the direction inwhich the rod 157 a of the third pneumatic cylinder 157 moves. The tipof the rod 157 a of the third pneumatic cylinder 157 is fixed to afixture plate 154 a fixed to the upper portion of the grip unit supportbase 154. Each of the pneumatic cylinders 155, 156, and 157 is alow-friction single rod double acting cylinder.

As shown in FIG. 6, both chambers of each of the pneumatic cylinders155, 156, and 157 are connected respective control ports of a five-port,flow-control servo valve 193 (five ports in total: one supply port, twocontrol ports, and two exhaust ports). A control signal is used toadjust the opening of one of the control ports of the servo valve 193,and hence adjust the flow from the supply port into one of the chambersof each of the pneumatic cylinders 155, 156, and 157. At the same time,the air in the other chamber is released from the other control portthrough the corresponding exhaust port to the atmosphere. The pressuredifference between both chambers of each of the pneumatic cylinders isthus controlled. Also, the internal pressure and displacement of thechambers are measured by a semiconductor type pressure sensor and arotary encoder respectively.

The thus configured holding unit 150 is a combination of a parallel linkmechanism and a gimbal mechanism, the parallel link mechanism havingthree degrees of freedom in total, that is, having the parallel links153 being rotatable around the parallel link support shaft 152 in thedirection φ (phi) in FIG. 6 in response to the motion of the firstpneumatic cylinder 155 and being rotatable in the direction φ in FIG. 6around the portions where the parallel link support shaft 152 and thelinks 153 a and 153 b are rotatably supported in response to the motionof the second pneumatic cylinder 156, and the grip unit support base 154being slidable in the direction ρ (rho) in FIG. 6 in response to themotion of the third pneumatic cylinder 157. The holding unit 150 cantherefore be designed in such a way that the trocar, which is set in theabdomen of the subject during laparoscopic surgery, is a stationarypoint. The holding unit is thus characterized in that it is notnecessary to directly support the forceps at the hole into which theforceps are inserted, so that the holding unit 150 can be operated withminimal burden on the body at the hole into which the forceps areinserted, and the position coordinates of the port of the trocar are notrequired in the kinetics computation. Further, a counterweight 159 isused to mechanically compensate part of the self-weight of the holdingunit 150.

The grip unit 160, which includes forceps 170 and a forceps holding unit180 as shown in FIGS. 5 and 7, is now described also with reference toFIG. 8, a perspective view showing the forceps 170, and FIG. 9, aperspective view showing the forceps holding unit 180. The forceps 170includes a rod-like forceps shaft 171, a forceps finger holder 172, andtwo forceps fingers 173 and 174. The rear end of the forceps shaft 171is rotatably supported by the forceps holding unit 180. One end of theforceps finger holder 172 is rotatably supported at the tip of theforceps shaft 171 around a rotating shaft 172 a disposed in a directionperpendicular to the axis of rotation of the forceps shaft 171. One endof each of the forceps fingers 173 and 174 is rotatably supported at theother end of the forceps finger holder 172 around rotating shafts 173 aand 174 a disposed in a direction perpendicular to the axis of rotationof the forceps shaft 171 and the rotating shaft 172 a of the forcepsfinger holder 172.

The forceps holding unit 180 includes a box-like holding body 181, fourpneumatic rotary actuators (pneumatic actuators) 182, 183, 184, and 185,four sets of rotary encoders and pressure sensors 186, 187, 188, and189, four drive pulleys 190, 191, 192, and 193, one driven pulley 194,and three direction conversion pulleys 195, 196, and 197. The holdingbody 181 is fixed to the grip unit support base 154 in the grip unit 150with screws. The forceps shaft 171 is inserted through and rotatablysupported by a bearing 181 b attached to a side 181 a of the holdingbody 181 in such a way that the bearing 181 b covers a hole provided inthe side 181 a, and the driven pulley 194 is attached to the rear end ofthe forceps shaft 171.

The first to fourth pneumatic rotary actuators 182, 183, 184, and 185include cylindrical bodies 182 a, 183 a, 184 a, and 185 a. Each of thebodies includes a swinging piece (not shown) having a shaft that islocated at the center of the body and can swing within a predeterminedangular range, the swinging piece extending from the swinging shaft tothe inner circumferential surface of the body, and a partition plate(not shown) extending from the swinging shaft to the innercircumferential surface of the body. By supplying and exhausting airthrough two kinds of ports, air supply/exhaust ports 182 b/182 c (183b/183 c, 184 b/184 c, 185 b/185 c) provided in the circumferentialsurface of the body 182 a (183 a, 184 a, 185 a), to and from the twochambers partitioned by the swinging piece and the partition plate so asto swing the swinging plate, a rotating shaft 182 d (183 d, 184 d, 185d) connected to the swinging shaft is rotated within a predeterminedangular range.

The first to third pneumatic rotary actuators 182, 183, and 184, towhich the first to third rotary encoders and pressure sensors 186, 187,and 188 are connected, are attached in line to a side 181 c, which isdisposed perpendicular to the side 181 a of the holding body 181, insuch a way that the rotating shafts 182 d, 183 d, and 184 d pass throughthree holes 181 d arranged in line in the side 181 c, and the first tothird drive pulleys 190, 191, and 192 are disposed in line and attachedto the tips of the rotating shafts 182 d, 183 d, and 184 d. The first tothird direction conversion pulleys 195, 196, and 197 are disposed insidethe side 181 c and rotatably supported next to the first to third drivepulleys 190, 191, and 192, respectively. Three loop wires (not shown)run from the first to third drive pulleys 190, 191, and 192 via thefirst to third direction conversion pulleys 195, 196, and 197 to therotating shaft 172 a of the forceps finger holder 172 and the rotatingshafts 173 a and 174 a of the two forceps fingers 173 and 174,respectively. The three loop wires thus engage the first to third drivepulleys 190, 191, and 192 as well as the rotating shaft 172 a of theforceps finger holder 172 and the rotating shafts 173 a and 174 a of thetwo forceps fingers 173 and 174, respectively.

The fourth swing pneumatic actuator 185, to which the fourth rotaryencoder and pressure sensor 189 is connected, is attached to the side181 a in such a way that the rotating shaft 185 d is oriented parallelto the forceps shaft 171 and passes through a hole provided in the side181 a of the holding body 181, and the fourth drive pulley 193 isdisposed next to the driven pulley 194 and attached to the tip of therotating shaft 185 d. A loop wire (not shown) engages the fourth drivepulley 193 and the driven pulley 194 so that the loop wire runs betweenthe fourth drive pulley 193 and the driven pulley 194.

The thus configured grip unit 160 is a 4-DOF wire mechanism for bending,gripping, and rotating, that is, having the forceps finger holder 172being rotatable around the rotating shaft 172 a in the direction ζ(zeta) in FIG. 8 in response to the motion of the first pneumatic rotaryactuator 182, the two forceps fingers 173 and 174 being rotatable aroundthe rotating shafts 173 a and 174 a in the direction η (eta) in FIG. 8in response to the motions of the second and third pneumatic rotaryactuators 183 and 184, and the forceps shaft 171 being rotatable aroundthe rotating shaft 185 d in the direction θ (theta) in FIGS. 8 and 9 inresponse to the motion of the fourth pneumatic rotary actuator 185. Theforceps 170 and the forceps holding unit 180 are therefore characterizedin that they are separable from each other in consideration of thedisinfection process.

FIG. 10 is a control block diagram of the multi-DOF forceps system 100of this embodiment. A 5-port spool servo valve 172 is used to drive thepneumatic cylinders 155, 156, and 157 and the pneumatic rotary actuators182, 183, 184, and 185.

Here, an external force acted on the above mentioned grip unit 160 (thetip of the forceps) can be estimated from the pressure differencebetween both chambers of each of the pneumatic cylinders 155, 156, and157 and the pneumatic rotary actuators 182, 183, 184, and 185 from therespective back-drivability. More specifically, first of all, from thepressure difference between the chambers of the pneumatic cylinders 155,156, and 157 as well as the pneumatic rotary actuators 182, 183, 184,and 185, all of which are pneumatic actuators, it is possible toestimate an external force Fext acting on the forceps fingers 173 and174, which form the tip of the slave manipulator 105 using a disturbanceobserver. The use of this control method requires an inverse dynamicsmodel of the whole portion including the pneumatic cylinders 155, 156,and 157, the pneumatic rotary actuators 182, 183, 184, and 185, and theforceps fingers 173 and 174. However on the forcepts in this embodiment,wires are used for power transmission, therefore, the modeling is noteasy due to friction of the wires and interference among the degrees offreedom. In this embodiment, to derive such a model, a neural network isused to learn a given arbitrary drive pattern.

Alternatively, It is also possible to estimate an external force actingon the forceps fingers 173 and 174, which form the tip of the slavemanipulator 105 from the drive force Fdr given to the pneumaticcylinders 155, 156, and 157 as well as the pneumatic rotary actuators182, 183, 184, and 185, which are pneumatic actuators.

In general, the response in a master-slave system will be ideal when theposition and the force of the master manipulator are the same as thoseof the slave manipulator. However, even when such an ideal response isachieved, and hence the operator feels as if he/she were directly doingoperation with his/her own hands, the performance of the operationtotally depends on the operator. To address such a problem, a bilateralcontrol system is used, in which impedance control applied to the mastermanipulator 101 differs from that applied to the slave manipulator 105.

The slave controller 107 makes use of the softness of the pneumaticcylinders 155, 156, and 157 and the pneumatic rotary actuators 182, 183,184, and 185 to apply a control method in which compliance is impartedto the slave manipulator 105. That is, since air can be compressed, theslave manipulator 105 has softness. Further, such softness is adjustableby adjusting the pressure of the compressed air.

The compliance of the slave manipulator 105 can prevent generation of anexcessive force. The softness of the slave manipulator 105 provides ashock absorbing effect when the slave manipulator 105 hits an objecthard.

In this case, when the slave manipulator 105 comes into contact with ahighly rigid environment, the deviation of the position of the mastermanipulator 101 from that of the slave manipulator 105 increases due tothe compliance. Even when the position of the master manipulator 101deviates from that of the slave manipulator 105, the operator can worknormally because the slave manipulator 105, which is used for surgery,primarily comes into contact with an organ and the operator works on theorgan while looking at images of the slave manipulator 105 through anendoscope.

On the other hand, the master manipulator 101 desirably operates in astably manner by imparting a moderate viscous effect. To this end, themaster controller 103 employs a position-based impedance control method(admittance control method) in which a force control loop includes amotion control loop in consideration of the characteristics of themotors 112, the first motor 122, the second motor 124, and the thirdmotor 126. The slave controller 107 employs a force-based impedancecontrol method in which a motion control loop includes a force controlloop because the pneumatic cylinders 155, 156, and 157 and the pneumaticrotary actuators 182, 183, 184, and 185 are characterized by highback-drivability and low stiffness.

This impedance control is explained as follows referring to FIG. 10.Reference numerals 1-8 in FIG. 10 correspond to the components 1-8according to the present invention shown in FIG. 13.

As shown in this figure, the master controller 103 and the slavecontroller 107 control the master manipulator 101 and the slavemanipulator 105, respectively, in such a way that the manipulators havethe following impedance characteristics.

For the slave manipulator 105,−fs=Kd(xs−xm)+Bd dxs/dt  (1)

For the master manipulator 101,fm−fs=Cd dxm/dt  (2)In the above equations,xs: the position and orientation of the tip (forceps fingers 173 and174) of the slave manipulator 105 (the position and orientationdetermined by the seven degrees of freedom)xm: the position and orientation of the tip (manipulation finger 132) ofthe master manipulator 101fs: the force that the tip of the slave manipulator 105 applies to theouter environmentfm: the force that the operator applies to the tip of the mastermanipulator 101Kd: the set stiffness of the slave manipulator 105Bd: the set viscosity of the slave manipulator 105Cd: the set viscosity of the master manipulator 101

To achieve the equation (1), impedance control including a force controlloop is applied to the slave manipulator 105. The equation of motion ofthe slave manipulator 105 is expressed in the joint coordinate system asfollows:τdr−Js(transposition)fs=Z(qs,dqs/dt,d ² qs/dt ²)  (3)In the above equation,τdr: the drive torque at each joint of the slave manipulatorZ: the inverse dynamics function for the slave manipulator 105qs: the displacement of each joint of the slave manipulator 105Js: the Jacobi matrix representing the transition from the displacementsof the joints to the displacement of the tip position of the slavemanipulator 105

To achieve the equation (1), the force fdr that the tip of the slavemanipulator 105 should produce and the target value τdrref of the drivetorque of each of the pneumatic cylinders 155, 156, and 157 and thepneumatic rotary actuators 182, 183, 184, and 185 are calculated asfollows:fdr=Kd(xs−xm)+Bd dxs/dt  (4)(in the frame 1 in FIG. 10 (Drive force calculation unit))τdrref=Js(transposition)fdr+Z(qs,dqs/dt,d ² qs/dt ²)  (5)(in the frame 2 in FIG. 10 (Drive force calculation unit))

Assuming that the dynamic characteristics of the pneumatic cylinders155, 156, and 157 and the pneumatic rotary actuators 182, 183, 184, and185 are satisfactory so that τdrref coincides with τdr, the equation (4)is substituted into the equation (5), which is then substituted into theequation (3) to derive the equation (1).

In practice, to prevent the equation (5) from being unstable due tophase retardation, the speed and acceleration among the inputs in theinverse dynamics model are determined from a target value of thetrajectory of the master manipulator 101 (in the frame 3 in FIG. 10(Inverse Dynamics Calculation Unit)). To produce the torque calculatedby using the equation (5) at each joint, mechanics computation is usedto convert the torque into the drive force target value Fdrref of eachof the pneumatic cylinders 155, 156, and 157 and the pneumatic rotaryactuators 182, 183, 184, and 185.Fdrref=Jaτdrref  (6)(in the frame 4 in FIG. 10 (Slave manipulator drive control unit))In the above equation,Ja: Jacobian representing the transition from the displacements of thepneumatic cylinders 155, 156, and 157 and the pneumatic rotary actuators182, 183, 184, and 185 to the displacements of the joint

Then, PI control is carried out to produce the drive force calculated byusing the equation (6).u=(Kap+Kai/s)(Fdrref−Fdr)  (7)(in the frame 5 in FIG. 10 (pneumatic actuator))In the above equation,u: the control voltage for the servo valve 172Kap: proportional gain Kai: integral gainFdr: the drive forces of the pneumatic cylinders 155, 156, and 157 andthe pneumatic rotary actuators 182, 183, 184, and 185 calculated frompressure values

Admittance control is applied to the master manipulator 101 to achievethe equation (2).dxm/dt=(fm−fs)/Cd  (8)(in the frame 6 in FIG. 10 (Master manipulator drive control unit))dqm/dt−Jm (inverse) dxm/dt  (9)(in the frame 7 in FIG. 10 (Master manipulator))

As seen from the equation (8), an input of the contact force (theexternal force acting on the forceps 173, 174) between the slavemanipulator 105 and the external environment is required. In thisembodiment, an external force (Fext) acting on the forceps 173, 174 atthe tip of the slave manipulator 105 is used, which is estimated, usingan disturbance observer, from a pressure difference between the chambersof each of pneumatic cylinders 155, 156, 157 and pneumatic rotaryactuators 182, 183, 184, 185, all of which are pneumatic actuators(inside the box with Reference number 8 in FIGS. 10 and 11 (Externalforce estimation unit)).

With respect to the estimation of an external force, when the impedancecontrol is applied to the slave manipulator 105, fdr coincides with fs,so a target drive force can be used as an estimated external force. FIG.12 is a block diagram showing an example of this case, and othercomponents are identical to those of FIG. 10. Therefore detailedexplanation is omitted for those.

According to the above configuration, the target drive force valueFdrref of each of the pneumatic cylinders 155, 156, and 157 and thepneumatic rotary actuators 182, 183, 184, and 185 can be produced in aquick and precise manner by the differential pressure control loop ineach of the cylinders and actuators. It is therefore possible tocompensate the characteristics disadvantageously affecting thepositioning, such as air compression properties and a deviation of theneutral point of the valve.

As described above, according to the multi-DOF forceps system 100 ofthis embodiment, the force acting on the slave manipulator 105 is fedback to the master manipulator 101 by operating the master manipulator101 primarily under electrically-driven speed control and the slavemanipulator 105 primarily under pneumatically-driven force control.Therefore, in the master manipulator 101, it is not necessary tocompensate for the dynamics and the self-weight of the mastermanipulator 101 in the motion range of the operator, allowing highlyaccurate, broadband positional control, which is specific to anelectrically-driven system, and in the slave manipulator 105,nonlinearity characteristics specific to a pneumatically-driven systempresents passive softness, provides a high mass-to-output ratio, andproduces a large force. Further, the slave manipulator 105, which isconfigured as a pneumatically-driven system, can be installed in anapparatus involving a magnetic field, for example, an MRI (MagneticResonance Imaging), and used in surgery.

Since the master manipulator 101 includes the 3-DOF translation unit 110and the 4-DOF orientation unit 120 connected to the translation unit110, and the slave manipulator 105 includes the 3-DOF holding unit 150and the 4-DOF grip unit 160 held by the holding unit 150, the motion ofthe human hand on the master manipulator 101 side can be reproduced onthe slave manipulator 105 side. Since the translation unit 110, theorientation unit 120, the holding unit 150, and the grip unit 160 areconfigured as the delta mechanism, the gimbal mechanism, the combinationof the parallel link mechanism and the gimbal mechanism, and the wiremechanism, respectively, the master manipulator 101 and the slavemanipulator 105 are configured differently from each other and theshapes thereof can be optimized in terms of operability. Since the gripunit 160 includes pneumatic rotary actuators 182, 183, 184, and 185 andwires connected to the pneumatic rotary actuators 182, 183, 184, and185, and the grip unit 160 is driven by pulling motions of the wires inresponse to the motions of the pneumatic rotary actuators 182, 183, 184,and 185, the grip unit 160 can directly transmit the swing motions ofthe pneumatic rotary actuators 182, 183, 184, and 185. Such aconfiguration allows reduction in weight of the slave manipulator 105.

Further, since the force acting on the grip unit 160 is set to beestimated from the pressure difference between chambers (FIG. 10) or thedrive force of each of the pneumatic cylinders 155, 156, and 157 and thepneumatic rotary actuators 182, 183, 184, and 185 by making use of theback drivability thereof, no force sensor is required on the grip unit160, thereby providing advantages of reducing the size of the grip unit160, making disinfection of the grip unit 160 easy, and eliminating theneed for calibration of the grip unit 160. Moreover, since thecompliance-based control is applied to the slave manipulator 105, theslave manipulator 105 will not produce an excessive force.

Since the position-based impedance control in which a force control loopincludes a motion control loop is applied to the master manipulator 101,and the force-based impedance control in which a motion control loopincludes a force control loop is applied to the slave manipulator 105,the slave manipulator 105 can be stably operated by imparting a moderateviscosity effect to the master manipulator 101. That is, the controlsystem according to this embodiment allows the operator to feel as ifhe/she pushes and pulls the master manipulator 101 fixed to a stationarywall via a damper. It is also possible to connect the master manipulator101 to the slave manipulator 105 via a spring and a damper. The valuesof the spring and the damper are adjustable by selecting the controlparameters.

In the embodiment described above, although the multi-DOF forceps system100 remotely controllable by means of wired communication has beendescribed, the multi-DOF forceps system 100 may be a system usingwireless communication or a system that is controllable from a nearbylocation. Further, although the multi-DOF forceps system 100 has beendescribed as an endoscopic surgery-assisting apparatus, the multi-DOFforceps system 100 can be configured as an apparatus for training adoctor or an apparatus for evaluating skill Although the invention hasbeen described with reference to the multi-DOF forceps system 100 usedin medical fields as a manipulation system having a force feedbackcapability, the invention is not limited thereto. The invention isgenerally applicable to various manufacturing fields.

What is claimed is:
 1. A manipulation system having a force feedbackcapability comprising a master manipulator and a slave manipulatorconnected to each other in a bilaterally controllable manner, wherein aposition and an orientation of a tip section of said slave manipulatoris controlled in accordance with manual operation on an input unit ofsaid master manipulator; said master manipulator is operated underelectrically-driven speed control and the slave manipulator is operatedunder pneumatically-driven force control, and an external force actingon the tip section of said slave manipulator is fed back in to saidmaster manipulator; and said slave manipulator comprises a drivemechanism for moving the tip section to a desired position with desireddegrees of freedom, and at least one pneumatic actuator for driving saiddrive mechanism; said manipulation system comprising: an external forceestimation section to estimate an external force acting on the tipsection of said slave manipulator from a motion of said pneumaticactuator; a master manipulator drive control unit to output, as areactive force given to the input unit, a force feedback of an externalforce acted on the tip section by driving the input section of saidslave manipulator based on the estimated value obtained, obtain a targetposition/orientation (xm) for the tip section of said slave manipulatorfrom an opposing force (fm) to the reactive force applied from the inputunit, and provide the obtained target position/orientation to said slavemanipulator; and a slave manipulator drive control unit to control theposition and orientation of the tip section of said slave manipulatorbased on the target position/orientation received from said mastermanipulator drive control unit.
 2. The manipulation system having aforce feedback capability of claim 1, wherein said slave manipulatorcomprises: a drive torque calculation unit to calculate a first drivetorque to be generated by said pneumatic actuator based on said targetposition/orientation received from the master manipulator; an inversedynamics calculation unit to obtain a second drive torque to begenerated by said pneumatic actuator, wherein speed generated by manualoperation on the input unit of the master manipulator and anacceleration speed obtained from the speed are used as input values andapplied in an equation representing an inverse dynamics of said slavemanipulator; a target drive torque calculation unit to obtain a targetdrive torque to be given to said pneumatic actuator from the first drivetorque obtained in the drive torque calculation unit and the seconddrive torque obtained in the inverse dynamics calculation unit; and apneumatic cylinder control unit for moving the position of said tipsection, by controlling an amount and speed of air supplied to acylinder based on the target drive torque obtained by the target drivetorque calculation unit, thereby moving the position of said tipsection.
 3. The manipulation system having a force feedback capabilityof claim 2, wherein said drive torque calculation unit calculates aforce (fdr) to be generated at the tip end of said slave manipulatorwith a formula offdr=Kd(xs−xm)+Bd dxs/dt wherein Kd is a set stiffness of the slavemanipulator, xs is a position and orientation of the tip end of theslave manipulator, xm is a position and orientation of the tip end ofthe master manipulator, and Bd is a set viscosity of the slavemanipulator; and wherein said inverse dynamics calculation unitcalculates the target drive torque value τdrref with an equation ofτdrref=−Js (transposition) fdr+Z(qs, dqs/dt, d²qs/dt²); wherein Js is aJacobi matrix representing a transition from the displacements of thejoints to the displacement of the tip position of the slave manipulator,Z is an inverse dynamics function for the slave manipulator, and qs is adisplacement of each joint of the slave manipulator; and wherein saidinverse dynamic calculation unit uses said target position/orientationreceived from the main manipulator control unit as a value for qs,dqs/dt, d²qs/dt², rather than the displacement value qs of the slavemanipulator.
 4. The manipulation system having a force feedbackcapability of claim 1, wherein said external force estimation unitestimates said external force from a pressure difference between bothchambers of said pneumatic actuator using a disturbance observerincluding an inverse dynamics model from said pneumatic actuator to thetip section.
 5. The manipulation system having a force feedbackcapability of claim 1, wherein the slave controller employs aforce-based impedance control in which a motion control loop includes aforce control loop; and said external force estimation unit estimatessaid external force from the first drive torque to be generated in saidpneumatic actuator based on said target position/orientation.
 6. Themanipulation system having a force feedback capability of claim 1,wherein the master manipulator includes a 3-DOF translation unit and a4-DOF orientation unit connected to the translation unit, and the slavemanipulator includes a 3-DOF holding unit and a 4-DOF grip unit held bythe holding unit.
 7. The manipulation system having a force feedbackcapability of claim 6, wherein the translation unit is configured as adelta mechanism, the orientation unit is configured as a gimbalmechanism, the holding unit is configured as a combination of a parallellink mechanism and a gimbal mechanism, and the grip unit is configuredas a wire mechanism.
 8. The manipulation system having a force feedbackcapability of claim 7, wherein the grip unit includes pneumatic rotaryactuators and wires connected to the pneumatic actuators, and the gripunit is driven by pulling motions of the wires in response to themotions of the pneumatic actuators.
 9. The manipulation system having aforce feedback capability of claim 1, wherein position-based impedancecontrol in which a force control loop includes a motion control loop isapplied to the master manipulator, and force-based impedance control inwhich a motion control loop includes a force control loop is applied tothe slave manipulator.
 10. The manipulation system having a forcefeedback capability of claim 1, wherein said slave manipulatorcomprises: a parallel link having: a parallel link support shaftrotatably supported on a base plate, a first link, one end of which isrotatably supported at said parallel link support shaft, a second linkparallel to said first link, one end of which is rotatably supported atsaid parallel link support shaft, a third link parallel to said parallellink support shaft, one end of which is rotatably supported at an otherend of said second link and at the same time a substantially centerportion of which is rotatably supported by said first link, a fourthlink parallel to said third link, one end of which is rotatablysupported at an other link of said first link, and a holding partrotatably supported at an other end of said third link and an other endof said fourth link; wherein a plane that goes through a rotational axisof an axis support section of said holding part and the third link andthat goes through a rotational axis of an axis support section of saidholding part and the fourth link is parallel to said first link; a firstpneumatic actuator to actuate said parallel link pivotably around saidparallel link support shaft; a second pneumatic actuator to actuate saidfirst link pivotably around an axis support section of said parallellink support shaft and said first link; a third pneumatic actuator toactuate a movable object slidable in a direction which goes through anintersection of a rotational axis of said parallel link support shaftand said plane, wherein an external force acting on said moving body isestimated using a back drivability of said first, second, or thirdpneumatic actuator from a respective movement thereof.